At a Glance

Why Get Tested?

To evaluate lung function by measuring blood pH, oxygen (O2) and carbon dioxide (CO2); to monitor treatment for lung diseases; to detect an acid-base imbalance in your blood, which may indicate a respiratory, metabolic, or kidney disorder; to evaluate the effectiveness of oxygen therapy

When to Get Tested?

When you have symptoms of a respiratory problem such as difficulty breathing, shortness of breath, or rapid breathing; when you are being treated for a lung disease; when an acid-base imbalance is suspected; periodically when you have a condition that causes an acute or chronic oxygen shortage and you are on oxygen therapy; during certain surgeries to monitor your blood's O2 and CO2 levels

Sample Required?

Most often a blood sample collected from an artery, usually the radial artery in your wrist; sometimes a blood sample drawn from a vein in your arm; capillary blood from a heelstick may be used for babies.

Test Preparation Needed?

Typically, none; however, if you are on oxygen therapy, the O2 may either be turned off for 20 to 30 minutes before the collection for a "Room Air" test. If this cannot be tolerated, or if your health practitioner wants to check your oxygen levels with the O2 on, the amount of oxygen being taken will be recorded.

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This article was last reviewed on October 24, 2013. | This article was last modified on December 29, 2014.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.